Operable Unit III Feasibility Study Report
IT Corporation (IT) prepared this Feasibility Study (FS) Report for Operable Unit III (OU III) at Brookhaven National Laboratory (BNL) under BNL Contract Number 710617. The FS Report was prepared in accordance with the tasks outlined in the OU III Remedial Investigation/ Feasibility Study Work Plan (IT, 1994) guidelines, criteria, and considerations specified in the National Contingency Plan (NCP) and the U.S. Environmental Protection Agency (USEPA) guidance document Guidance for Conducting Remedial Investigations and Feasibility Studies Under CERCLA (USEPA, 1988).
The OU III FS Report documents the basis and procedures used in identifying, developing, screening, and evaluating remedial alternatives and removal actions to mitigate contamination at OU III. The report provides BNL, USEPA, and NYSDEC with sufficient data to select a feasible and cost-effective remedial alternative that will protect human health and the environment.
E.2 Summary of the Remedial Investigation
The BNL OU III Remedial Investigation (RI) Report characterized the physical conditions at OU III, the nature and extent of contaminant migration, and the potential current and future risks to human health and the environment for OU III. Sixteen AOCs and four additional areas of investigation (AAIs) were evaluated in the OU III RI Report. These AOCs and AAIs include the following three categories: (1) eleven AOCs that are designated in the Response Strategy Document (SAIC, 1992) and Interagency Agreement (IAG); (2) four AOCs of OU II/VII where groundwater remains a potential concern; and (3) one AOC and four AAIs addressing potential site-wide source areas of groundwater contamination that are not included in the above two categories.
During the original remedial investigations in 1995 and 1996, the impacts on the groundwater from 11 AOCs in Operable Unit III and the four AOCs located in Operable Unit II/VII were evaluated together with Operable Unit III. Based upon the discovery in late 1996 of tritium in groundwater, one additional AOC and four additional areas of investigation were added to the remedial investigation in 1997. A brief listing of the 16 AOCs and four additional areas of investigation included in Operable Unit (OU) III is as follows:
- Sub-AOC 15A: Potable and Supply Well Numbers 1, 2, 3, 4, 6, 7, 10, 11, and 12
- Sub-AOC 15B: Monitoring Well 130-02
- Sub-AOC 24A: Process Supply Wells 104 and 105 (groundwater samples collected)
- Sub-AOC 24B: Recharge Basin HP, Medical Center Reactor (soil and sediment samples collected)
- Sub-AOC 24C: Recharge Basin HN, Alternating Gradient Synchrotron (AGS) (surface water and sediment samples collected)
The AOCs noted above that only address groundwater have been previously investigated and/or had their sources removed such that only groundwater remains a potential concern. OU III was developed to address groundwater plumes originating from the western portion of the site; all potential sources in this area require evaluation for their impact to groundwater. Thus, the AOCs included in OU II/VII were also evaluated in OU III in terms of groundwater impact only. The OU II/VII source investigation was addressed and is presented in the February 1999 OU II/VII RI Report. The OU II/VII AOCs included in this RI are as follows:
- Sub-AOC 9A: Canal
- Sub-AOC 9B: Underground Duct Work
- Sub-AOC 9C: Spill Sites
- Sub-AOC 10A: Tanks D1, D2, and D3
- Sub-AOC 10B: Underground Pipelines
The AOCs listed above were originally investigated in 1995 and 1996. However, based on the results and indications of other potential sitewide sources of groundwater contamination, five additional areas of investigation (AAI) were incorporated into the OU III remedial investigation 1997. One of these five AAIs (AOC 29 - High Flux Beam Reactor (HFBR)/Spent Fuel Pool (SPF) Tritium Plume) was upgraded to an AOC and is discussed in this report as a separate AOC.
This AOC and the remaining four AAIs are as follows:
These AOCs/AAIs (with the associated media) were investigated to define the nature and extent of contamination, to evaluate potential current and future risks to human health and the environment, and to support the development of a comprehensive FS Report. The FS Report will evaluate proposed remedial actions for all AOCs and associated media that pose an unacceptable risk to human health or the environment. The recommended remedial actions resulting from the FS Report will be documented in the OU III Record of Decision (ROD). Table E-1(at the end of executive summary) summarizes the selected remedies for each AOC and AAI.
E.2.1 Nature and Extent of Contamination and Risk Assessment
The OU III field investigations were conducted from October 1995 through December 1997. Sampling and analyses consisted of geophysical logging, radiological surveys, Geoprobe soil sampling, monitoring well borings, Geoprobe groundwater sampling, monitoring well groundwater sampling, supply well sampling, surface water sampling, and sediment sampling.
E.2.1.1 Surface Soil Contamination
Surface soil samples from OU III did not reveal any significant contamination. Most inorganic analytes were detected at concentrations less than or slightly above the screening/background concentration. Thallium and mercury were detected at elevated levels in the samples collected from the Building 830 Pipe Leak (AOC 11/12). Copper and manganese were detected at elevated concentrations in AOC24B, the HP Recharge Basin, which indicated that further evaluation may be required. However, based on the risk assessments, exposure to inorganics in soils were found not to pose an unacceptable risk to human health or the environment.
Volatile organic compounds, pesticides, and polychlorinated biphenyls (PCBs) were not detected at concentrations above the screening levels. Benzo(a)pyrene was the only semivolatile organic
compound detected at a concentration of more than two times the screening concentration, specifically, at two samples from the trichloroethene (TCE) Spill Area (AOC 19). Polycyclic aromatic hydrocarbons, such as benzo(a)pyrene, are common in industrial/commercial areas. They can enter the environment as releases from forest fires, wood burning, and truck/automobile exhaust. However, based on the risk assessments, exposure to these organic contaminants in soils was an acceptable risk for humans and the environment.
Cesium-137 was the only radionuclide whose activity exceeded the screening concentration; it was detected at activities of approximately three times the screening level in two samples collected from the Building 830 Pipe Leak (AOC 11/12). These activities indicate that cesium-137 in the AOC 11/12 area may be of concern. The risk assessments also indicated that exposure to cesium-137 in soils may pose a marginally unacceptable risk to human-health. Removal of the contamination at AOC 11/12 Building 830 is in progress to address this concern (see Section 2.5.3).
E.2.1.2 Subsurface Soil Contamination
The average concentrations of most analytes found in subsurface soils for each area of concern typically were below the chemical screening concentration. The only analytes at concentrations above screening concentrations that may warrant further study were lead, mercury, manganese, nickel, thallium, benzo(a)pyrene, and cesium-137. However, lead was only detected at an elevated concentration in one sample, indicating that it is not a significant concern. The average concentration of nickel in AOC 11/12 was 22.1 mg/kg, which is within the range of background nickel concentrations for the eastern United States (0.5 to 25 mg/kg). The elevated levels of manganese were only found in the Recharge Basins HP. Thallium was consistently detected in the subsurface soil samples at concentrations of up to eight times the screening/background concentration. Additionally, the average concentration in each area of concern was greater than the screening/background concentration, indicating that elevated thallium concentrations are a potential concern. However, exposure to inorganics in the soil was not identified as a concern in the risk assessment.
Concentrations of benzo(a)pyrene were up to six times the screening concentration in samples collected from the Old Firehouse. In addition, the average concentration also was greater than the screening level. However, based on the risk assessments, exposure to benzo(a)pyrene in subsurface soil did not pose an unacceptable risk to human health or the environment. Cesium-137 was at an elevated level in one of the subsurface soil samples from AOC 11/12. This sample was collected proximate to the surface soil samples that also contained elevated levels of cesium-137, indicating that further evaluation may be warranted in this area. However, based on the risk assessment, exposure to cesium-137 in subsurface soil did not pose an unacceptable risk to human health or the environment.
E.2.1.3 Groundwater Contamination
Four groundwater sampling zones were established to evaluate the vertical extent of contamination: (1) water table zone, (2) mid-glacial zone, (3) deep glacial zone, and (4) Magothy zone. The water table zone extends from a depth of zero to 50 feet above mean sea level (msl), the mid-glacial zone from zero to 60 feet below msl, the deep glacial zone from 60 to 150 feet below msl, and the Magothy sampling zone from 150 to 250 feet below msl. The evaluation of groundwater quality was based on the analytical results from permanent monitoring wells and Geoprobesô along with geologic interpretations, supplemented by the analyses from temporary wells. The primary concerns identified in groundwater were the elevated levels of volatile organic compounds (VOCs), strontium-90, and tritium. For VOCs, three primary plumes were identified: (1) carbon tetrachloride in the deep glacial zone;
(2) tetrachloroethene (PCE) and 1,1,1-trichloroethane (TCA) contamination extending from the water table zone between Building 96 and Brookhaven Avenue into the deep-glacial zone; and (3) TCA contamination near the AGS and the WCF in the water table zone. Since carbon tetrachloride was primarily found in the deep glacial zone, its exact source is not yet known. The primary source of VOC contamination appears to have been near Building 96, which was used as a truck wash station and/or drum storage area. However, additional investigations of the source are being performed under the PA/SI, the Facility Site Review, the SCDHS Database Review and the Historical Site Review.
The carbon tetrachloride plume was primarily found in the deep glacial zone, extending from south of Princeton Avenue to just south of Moriches-Middle Island Road. However, the vertical extent of contamination in the Magothy zone is not fully delineated and further characterization is planned. The exact source of the carbon tetrachloride was not identified, however, since the carbon tetrachloride has traveled a great distance from the source, the exact source may never be confirmed. The upgradient extent of the carbon tetrachloride plume lies between Princeton Avenue and the Middle Road. The monitoring wells, vertical profiles, and Geoprobes upgradient of the plume have shown no evidence of any continuing source of carbon tetrachloride. Speculations on the plausible sources include the Supply & Material area, Building 208, Building 96 area, the old Chemistry Buildings, the old gasoline station, and the former carbon tetrachloride underground storage tank. None of the wells, Geoprobes, or vertical profiles detected any evidence of a continuing source corresponding to the carbon tetrachloride plume. Since the use of carbon tetrachloride as an industrial chemical pre-dates the use of the more modern TCE and PCE it seems likely that it was released into the environment years ago. The commercial use of carbon tetrachloride dates back to at least the 1920s. It is not known if carbon tetrachloride was used by the Army at Camp Upton.
The source of the PCE contamination is believed to be the area south of Building 96, which was used as a truck-wash station and, reportedly, a drum storage area/scrapyard. The PCE plume extends from the area south of Building 96 to BNL's south boundary. Vertically, this plume extends from the water table to approximately 140 feet below msl. Elevated levels of TCA were frequently detected in the water table zone centered around the AGS, Building 96, and Building 208. In the mid-glacial zone, high concentrations of TCA were found on Rowland Street, Weaver Street, and south of Princeton Avenue at monitoring well cluster OSC-MW05. TCA contamination in the deep glacial zone was limited to the area at the south boundary.
There are three strontium-90 plumes on site. The first, located south of the BGRR, is approximately 500 feet wide and 1,000 feet long. The second plume contains two plumes from different sources. The northern source area is the WCF (Building 811) and associated tanks and pipelines; the second source is the Building 801 Pile Fan Sump. The WCF/Building 801 PFS plume is approximately 500 feet wide and 2,000 feet long, extending in a north-south direction from the WCF to Cornell Avenue. The third plume includes small localized areas of contamination at the Glass Holes/HWMF area. The highest strontium concentration was detected at the Glass Holes area.
Tritium plume concentrations greater than 20,000 pCi/l in the groundwater extend from the HFBR to just south of Rowland Street. The downgradient edge of the plume defined by the 1,000 pCi/l contour extends just past Princeton Avenue. The highest tritium activity detected in this plume is 1,590,000 pCi/l (see Appendix B). Tritium activities at the downgradient edge of the plume range between 1,000 and 5,000 pCi/l . There is also a second area with tritium activities greater than the drinking water standard (20,000 pCi/l ) immediately north of the HFBR Stack. Isolated areas of gross beta, radium-226, strontium-90, and inorganic contamination also were identified. Elevated concentrations of inorganics, primarily lead, which may warrant further evaluations, were detected between the Bubble Chamber and the north end of the LINAC. However, semivolatile organic compounds, pesticides, and PCBs were not identified as a concern in the groundwater in the OU III study area.
Based on the risk assessments, exposure to contaminants associated with groundwater plumes (TCE, PCA, carbon tetrachloride, Sr-90, and tritium) may pose potential risks to human health. This issue of groundwater contamination is discussed in this FS Report.
E.2.1.4 Surface Water Contamination
Three recharge basins were sampled for surface water as part of OU III: Recharge Basin HZ in AOC 14, and the two Recharge Basins HN in sub-AOC 24C. Recharge Basin HZ receives runoff from the northern portion of AOC 14 via a ditch. Several polycyclic aromatic hydrocarbons were detected in its surface water, which may be related to local truck/automobile traffic. However, only one polyaromatic hydrocarbon (PAH), benzo(a)pyrene, exceeded screening criteria. Storm water runoff from local roads and parking lots contains oil and grease that may be a source of semivolatile contamination in surface water samples.
Recharge Basins HN are located within the Relativistic Heavy Ion Collider (RHIC) ring and received non-contact cooling water from the AGS. There is no evidence of contamination of these basins from radioactive wastewater discharges; however, iron and copper were at elevated levels. Iron was at approximately twice the screening criteria in both basins, and copper was at eight to nine times the screening level in all three surface water samples. The risk assessments indicate that exposure to these contaminants in surface water do not pose an unacceptable risk to human health or the environment.
E.2.1.5 Sediment Contamination
Nine sediment samples were collected from an inactive cesspool and six recharge basins: one sample from Recharge Basin HZ in AOC 14, three samples from Recharge Basin HT in AOC 20, one sample each from the two Recharge Basins HP in sub-AOC 24B, one sample each from the two Recharge Basins HN in sub-AOC 24C, and one sample from an inactive cesspool in AOC 7. Except for the samples collected from Recharge Basin HT, all sediment samples contained analytes at concentrations of less than twice the screening level. Concentrations in two samples collected from basins HT were approximately 6 to 10 times the screening concentration of 0.71 mg/kg for mercury. In addition, they had elevated levels of copper, lead, silver, and zinc. These two samples were collected from a location away from the outfall of Recharge Basin HT. Although the sediment sample collected near the outfall of Recharge Basin HT did not contain inorganic contamination, it had elevated levels of PAHs and one pesticide, delta-benzene hexachloride (BHC). Recharge Basin HT receives runoff from the LINAC area where there are contaminated landscaping soils. Storm water runoff from local roads and parking lots contain oil and grease that may be a source of semi-volatile contamination in sediment samples from the Recharge Basin HT. However, from the risk assessments, exposure to these contaminants in sediment was not found to pose an unacceptable risk to human health or the environment.
E.2.2 Remedial Action Objectives (RAO)
Based on evaluations of the nature and extent of contamination, and groundwater transport modeling, it can be concluded that on-site and off-site groundwater contains several constituents at concentrations which exceed ARARs (i.e., New York State Groundwater Quality Standards and Federal MCLs). The human health risk assessment on groundwater indicate that the primary contaminants associated with groundwater plumes may pose unacceptable risks to current off-site residents and future hypothetical on-site residents. Accordingly, the following RAOs were identified:
E.3 Summary of Interim Removal/Remedial Actions
The following interim actions were undertaken within the OU III study area: the on-site OU III southern boundary groundwater Interim Removal Action (IRA), the off-site OU III industrial complex groundwater IRA, the off-site public water hookup interim action, the tritium groundwater IRA, and additional source removal actions The OU III southern boundary groundwater Interim Removal Action (IRA) is being carried out in response to the detection during the RI of elevated concentrations of VOCs within the OU III study area and off-site of OU III. The groundwater IRA addresses the off-site migration of VOC contaminated groundwater exceeding 50 ppb. Its design objective is to capture, contain, and prevent further downgradient migration of this VOC contaminated groundwater by installing a groundwater recovery system at the southern boundary. This system consists of six extraction wells located along the southern side of the southern boundary road, an air stripper to treat recovered water, and discharge of the treated groundwater to a newly constructed recharge basin next to the HP basins south of the medical reactor. The design and details of the groundwater extraction and treatment system are documented in a Pre-Design Investigation Report (IT Corp., 1997) and in the Remedial Design Workplan (RDWP).
The OU III industrial complex groundwater Interim Removal Action (IRA) will be conducted to deal with a plume of volatile organic compounds found in the off-site groundwater during the OU III RI. This interim removal action addresses the control and mitigation of off-site migration of the highest concentrations of the deep VOC plume beyond the industrial complex located south of OU III. The objective of this groundwater IRA is to hydraulically control and treat groundwater containing the highest concentrations of VOCs identified off-site, and to prevent its further migration beyond the industrial complex. As detailed in a Pre-Design Report (Geraghty & Miller Inc., November 1997), in-well stripping was selected as the remedial technology. The system would consist of seven in-well stripping wells variably spaced along the southern side of the industrial complex each of which would pump at approximately 100 gpm. VOCs concentrations in groundwater that were detected on-site and off-site of the OU III study area exceeded Federal MCLs and NYSDEC groundwater quality standards. In response, public water hookups were provided to residents downgradient of OU III and OU I who use private wells for drinking water. The public water hookups are a precautionary measure to prevent potential exposure to groundwater contamination.
Tritium was detected in groundwater adjacent to the HFBR facility in late 1996 at levels above the Environmental Protection Agency's (EPA) drinking water standard of 20,000 pCi/l . The major source of tritium was the leaking Spent Fuel Pool (SFP), and spills of primary coolant that have leaked into the floor. Through evaluation of groundwater flow, radioactive decay, dispersion, and groundwater modeling, it is estimated that tritium concentrations above 20,000 pCi/l from the HFBR tritium plume will never cross the BNL boundary. Nevertheless, a groundwater IRA was implemented consisting of the following: (1) removing the spent fuel elements, pool equipment, pool water, and installation of an impervious liner, (2) eliminating other potential sources of leakage by bringing the HFBR/SFP into compliance with Suffolk County Department of Health Services Article 12, and (3) installing a groundwater extraction and recirculation system south of the HFBR to intercept the plume and ensure that tritium above the USEPA drinking water standard will not migrate across the BNL boundary.
Additional source removal actions that were implemented to improve groundwater quality within OU III were the removal of the cesspools/septic tanks, the strontium-90 source removal actions, and the removal of Building 830 underground storage tanks.
E.4 Identification and Evaluation of Remedial Alternatives
For the purposes of this report, groundwater contamination was separated into three areas according to the type and location of contaminants. These three areas include: (1) the on-site and off-site VOC contamination, (2) the on-site strontium-90 contamination in the water table zone present at the BGRR/WCF and the Glass Holes/HWMF areas, and (3) the tritium plume in the vicinity of the HFBR.
Preliminary remediation goals (PRGs) were established to achieve the remedial action objectives, and to develop, screen, and analyze remedial alternatives. PRGs for groundwater represent the most stringent of the Federal MCLs and NYSDEC Groundwater Quality Standards which are designed to protect the best usage of groundwater as a potential source of potable water. Because remediating groundwater to PRGs may be technically and economically impractical, and most residents located downgradient of BNL are hooked up to public water, groundwater treatment can be combined with natural attenuation to address the impacted areas. General response actions (GRAs) were identified that would address the RAOs. GRAs include no action, institutional actions, containment, treatment, and disposal. For each GRA, the options for technology types and process were identified and screened for their technical feasibility. The options retained were assembled into remedial action alternatives for each of the three contaminated areas. These alternatives were further evaluated for their effectiveness, implementability, and cost to identify those that could be evaluated in detail.
E.4.1 Description of Remedial Alternatives Evaluated in Detail
Tables E-2 through E-4 summarize the detailed evaluations of the strontium, tritium and VOC remedial alternatives. A brief description of these alternatives are given below:
Strontium Remedial Alternatives:
Alternative S1 - No Action. The no action alternative does not include any remedial activities. In accordance with the NCP, the no action alternative is required to be carried through the detailed analysis of alternatives to form a baseline for comparing with all other alternatives.
Alternative S2 - Natural Attenuation. Under this alternative, the strontium contaminated groundwater will be reduced to PRGs via natural attenuation processes such as radioactive decay, dilution, and dispersion. These natural processes would be monitored to ensure that the contaminant's mass, toxicity, and mobility are falling to levels that are protective of human health and the environment. Sixty monitoring wells will be sampled and analyzed for strontium semiannually for the first 5 years and annually thereafter for a total of 60 years.
Alternative S4 -In Situ Precipitation. In this innovative alternative, a two-step in-situ chemical precipitation contains the strontium-90 plume at the BGRR/WCF/PFS and the Glass Holes/HWMF Area. In the first step, solutions with dissolved phosphate are forced through the groundwater and soil, via injection wells, to react with the strontium contaminants, and convert them to less soluble or less mobile compounds. Phosphate salts of strontium are very insoluble. In the second step, solutions of lime are injected into the aquifer to form calcium hydroxyapatite (a calcium phosphate) which can also co-precipitate or adsorb the strontium.
Alternative S5a -Groundwater Extraction/Ion Exchange/On-Site Discharge. This alternative involves the containment and extraction of groundwater containing the highest concentrations of Sr-90 from the hot spots at the PFS, WCF, and the Glass Holes, treating the extracted water via ion exchange beds, and then discharging it to recharge basins.
Groundwater extraction and hydraulic control may be accomplished by installing three recovery wells; one well located within the WCF hot spot, one near the PFS hot spot, and another located south of the Glass Holes hot spot. Two groundwater treatment systems will be required, one at the Glass Holes area and another at the WCF/PFS area. After treatment via ion exchange, groundwater from the Glass Holes system and the WCF/PFS system will be pumped to the RA V basin and HX basin, respectively. The spent ion exchange media will be transported and disposed off-site.
Alternative S7 -Groundwater Extraction/Ion Exchange/On-Site Discharge/Permeable Reactive Wall. This "hybrid" alternative combines extraction and treatment of groundwater at the WCF/PFS plume (Alternative S5a) with a Permeable Reactive Barrier (PRB) at the Glass Holes area (Alternative S3). The "pump and treat" system at the WCF/PFS area will be identical to the system for Alternative S5a. Groundwater will be extracted from 2 wells at 140 gpm, strontium will be removed by adsorption on UOP A-51 synthetic zeolite, and the groundwater, with strontium-90 now below the MCL, will be discharged to the HX basin for recharge to the aquifer.
Slurry wall construction techniques will be used to install the PRB of clinoptilolite in the aquifer, downgradient of the Glass Holes Plume. The PRB will be 240 feet long by 42 feet deep and 3 feet thick. This wall is expected to adsorb the strontium from the Glass Holes plume for at least 25 years as it migrates downgradient.
Tritium Remedial Alternatives:
Alternative T1 - No Action. The no action alternative does not include any remediation. In accordance with the NCP, the no action alternative is required to be carried through the detailed analysis of alternatives to form a baseline of comparison for the other alternatives.
Alternative T2 - Natural Attenuation. Under this alternative, tritium contamination in the groundwater would decrease over time through natural processes without any controls, removal, treatment, or other mitigating actions. These natural processes would be monitored to ensure that the contaminant's mass, toxicity, and mobility are falling to levels that are protective of human health and the environment. This alternative assumes that the existing tritium recovery system will be deactivated.
Alternative T3 - Natural Attenuation with the Tritium IRA System. This alternative will consist of the continued operation of the tritium IRA together with natural attenuation. Natural attenuation is the process by which concentrations of tritium will decrease in the groundwater by diffusion, dilution, and radioactive decay. Natural attenuation can effectively reduce a contaminant's toxicity, mobility, and volume to levels that protect human health and the environment.
Alternative T4 - Contingency based Remediation. This alternative relies on natural attenuation to lower the tritium contamination present in the Upper Glacial aquifer south of the HFBR; it is similar to Alternative T2 with the Princeton Avenue IRA being placed in stand-by. However, active remediation through hot spot removal at the HFBR and/or reactivation of the Princeton Avenue IRA system will occur if tritium concentrations significantly change from the groundwater monitoring data. Two specific contingencies have been identified for this alternative: (1) Removal and off-site disposal of tritium Hot spots through micro-pumping at the base of the reactor if verified concentrations in front of the reactor exceed 2,000,000 pCi/l , and (2) reactivation of the Princeton Avenue IRA if verified concentrations of tritium at Chilled Water Plant Road exceed 25,000 pCi/l .
Alternative T5 - Extraction/Recirculation. This alternative involves controlling the tritium plume's migration by extracting and recirculating the tritium contaminated groundwater. The three components of this alternative are extracting the groundwater from the vicinity of the southern edge of the 20,000 pCi/l tritium plume, removing trace VOCs by carbon adsorption from the extracted water, and discharging the water into the RA V basin. Extraction would control the migration of the portion of the tritium plume that exceeds MCLs which can be accomplished with four extraction wells.
Alternative T6 - Continuous Hot Spot Removal/On-Site Storage. This alternative involves extracting groundwater from the tritium hot spot in the immediate vicinity of the HFBR, storing the extracted groundwater on-site until the water naturally decays to below drinking water standards over a 50 year timeframe, and then discharging the water into recharge basin RA V. Groundwater would be extracted from two extraction wells located downgradient of the HFBR and pumped into a 1.2 million gallon storage tank.
Alternative T7 - Continuous Hot Spot Removal/Off-Site Disposal. This alternative involves installing the same groundwater extraction system discussed in Alternative T6. However, instead of on-site storage, the tritiated water will be disposed off-site. The most likely method of disposal will be evaporation. The extracted groundwater will be transferred directly to a 20,000 gallon feed tank that will discharge into tanker trucks which will be transported to an off-site disposal facility for evaporation. No residuals will generated as a result of this alternative, as all groundwater will be evaporated off-site. This alternative also assumes that the tritium IRA will be deactivated.
Alternative T8 - Continuous Hot Spot Removal/On-Site Evaporation. This alternative includes the installation of the same groundwater extraction system discussed in Alternative T6 and T7. However, the tritiated groundwater will be evaporated on-site. The evaporator will evaporate the tritium-containing water to the atmosphere from a stack 70 feet from the base of the evaporator skid. Based on simulated tritium concentrations in the influent, the total amount of tritium within the 1,000,000 gallons of extracted water is 1.6 curies which will be evaporated throughout the course of the year. The current HFBR stack, which is not currently in operation, has a permitted discharge limit of 100 curies per year . Therefore, the discharge of tritium to atmosphere is well within the permitted discharge limit for BNL. No residuals will be produced from this process as all water will be evaporated into the atmosphere. This alternative also assumes that the tritium IRA will be de-activated.
VOC Remedial Alternatives:
Due to the depth to VOC contaminants in the groundwater, type of contaminants, and type of geology, only two groundwater remedial technologies were evaluated for the development of alternatives; groundwater extraction and treatment; and in situ in-well stripping. Specific treatment technologies evaluated include air stripping, carbon adsorption, and UV oxidation. VOC remedial alternatives were developed based on varying the remedial capture goals (RCGs) of treatment wells which determined the number and placement of wells for the alternatives. The RCG is a design tool used for groundwater modeling to determine optimum placement of remediation wells which would actively remediate the groundwater. RCG is not considered the cleanup goal. Various RCGs were utilized for the development of VOC alternatives which were based on the number and placement of the remediation wells. However, the ultimate goal of any alternative is the restoration of the Upper Glacial Aquifer to drinking water standards (PRGs) within 30 years.
VOC alternatives do not directly remediate the VOC contamination present in the Magothy aquifer. Alternatives focus on the restoration of the Upper Glacial aquifer due to the higher velocity of groundwater, more potential receptors, and increased potential for VOC plume growth and migration. The remediation of the Upper Glacial aquifer will also result in the reduction of VOCs migrating into the Magothy, thus resulting in less impact to the Magothy Aquifer. The direct remediation of the Magothy will be difficult due to the slower groundwater velocities and the depth to groundwater within this zone. Simulated VOC concentrations for the Magothy Aquifer indicate that VOCs will still be present above drinking water standards for all alternatives after 60 years. At present, limited characterization of the Magothy Aquifer has been performed, and additional characterization and monitoring wells are planned. Upon completion of this characterization and monitoring, the selected remedy for the Magothy Aquifer will be reevaluated. All VOC remedial alternatives include the continued operation of the Southern Boundary and Industrial Complex IRA systems, along with the installation and operation of a VOC source removal system south of Building 96. For the purposes of this FS, an air sparging/soil vapor extraction (AS/SVE) system was chosen as the remedy for this area. However, further characterization and delineation is on-going. The final design and implementation of the source removal system south of Building 96 will be based on the results of the characterization, and will be implemented as an Interim Removal Action.
Alternative V1 - No Action. No active remediation will be conducted under this alternative. It is expected that, over time, the plume will continue to migrate further down-gradient of the site and potentially impact receptors. Institutional controls which have already been implemented include off-site public water hook-ups. This alternative represents the current conditions at the site, and comparison for the other alternatives. Regulatory requirements mandate the detailed evaluation of the No Action alternative.
Alternative V2 - Natural Attenuation. This alternative addresses the on-site and off- site VOC plume attributed to OU III and OU I/IV through a combination of the following: the continued operation of the Southern Boundary groundwater treatment system (on-site IRA) to capture and contain groundwater with VOCs greater than 50 ppb, the treatment of the VOC source area (Building 96) via an AS/SVE system, the operation of the Industrial Complex off-site IRA system, off-site public water hookups for the entire residential area affected by the plume, and the natural attenuation to PRG levels of on-site and off-site contamination that is not captured by the IRA systems. The natural attenuation portion of this alternative consists of establishing a groundwater monitoring program to monitor the rate of degradation/attenuation and migration of on and off-site VOCs.
Alternative V7 - On-Site In-Well Stripping (Six Wells)/Off-Site In-Well Stripping (18 Wells). This remedial alternative will address the OU III, OUs I/IV, RA V hot spot area plumes, and OU III and OUs I/IV plumes downgradient near Brookhaven Airport. It consists of the following: an on-site AS/SVE source removal system; the installation of an on-site in-well stripping system at Middle Road; the continued operation of the on-site Southern Boundary IRA treatment system; the off-site Industrial Complex IRA treatment system; the installation of off-site in-well stripping systems, and the implementation of a groundwater monitoring program. The off-site treatment wells consist of wells located at North Street (3 wells), Brookhaven Airport (8 wells), LIPA right-of-way (one well), Industrial Complex low level plume (2 wells), and RA V plume (4 wells). The Industrial Complex IRA system is currently under construction with an anticipated start-up date of July 1999. All VOCs that are outside the capture limits of the treatment systems will decline through natural attenuation.
Alternative V10b - On-Site In-Well Stripping (Four Wells)/Off-Site In-Well Stripping (16 Wells). This remedial alternative consists of the following components: installation of a source removal system at Building 96; an on-site in-well stripping system at Middle Road; the continued operation of the on-site Southern Boundary IRA treatment system, the off-site Industrial Complex IRA treatment system; an off-site in-well stripping system; off-site public water hookups; and a groundwater monitoring program. The off-site treatment wells consist of wells located at North Street (4 wells), Brookhaven Airport (7 wells), LIPA right-of-way (3 wells), Industrial Complex east (one well), and RA V plume (one well). All VOCs on site and off site outside the capture limits of the remedial systems will attenuate naturally. Although the Southern Boundary IRA and the public water hook-up of off-site residences have been accomplished, they are considered an integral component of this alternative for addressing the entire on-site and off-site VOC plume. The Industrial Complex IRA system is under construction with an anticipated start-up date of July 1999.
Alternative V10c - On-Site In-Well Stripping(Six Wells)/Off-Site In-Well Stripping (16 Wells). This remedial alternative consists of several parts: the installation of a source removal system at Building 96; an on-site in-well stripping system at Middle Road; an on-site in-well stripping system for the OU III low level VOC plume; the continued operation of the on-site Southern Boundary IRA treatment system, the off-site Industrial Complex IRA treatment system; an off-site in-well stripping system; and the off-site public water hookup program. The off-site treatment wells consist of wells located at North Street (4 wells), Brookhaven Airport (7 wells), LIPA right-of-way (3 wells), Industrial Complex east (one well), and RA V plume (one well) Also, a groundwater monitoring program will be implemented. All VOCs on-site and off-site outside the capture limits of the remedial systems will attenuate naturally. Although the Southern Boundary IRA and the public water hook-up of off-site residences have already been implemented, they are considered an integral component of this alternative for dealing with the entire on-site and off-site VOC plume. The Industrial Complex IRA system is under construction with an anticipated start-up date of July 1999.
Alternative V11 - On-Site In-Well Stripping/Off-Site In-Well Stripping at Non-Residential Areas. This remedial alternative consists of installing a source removal system at Building 96, using an on-site in-well stripping system at Middle Road, the continued operation of the on-site Southern Boundary IRA and Industrial Complex IRA treatment systems, off-site in-well stripping sub-systems, and off-site public water hookups. The off-site treatment wells consist of wells located at North Street (3 wells), Brookhaven Airport (10 wells), Industrial Complex east (one well), and RA V plume (one well). A groundwater monitoring program will also be implemented. All VOCs on-site and off-site outside the capture limits of the remedial systems will attenuate naturally. The goals of this alternative are to contain and capture existing off-site groundwater contamination areas by locating remedial systems in non-residential areas and determining the impacts on plume migration and assuming compliance with RAOs
Alternative V13 - On-Site and Off-Site Extraction/Air Stripping/On-Site Discharge. This remedial alternative consists of the following: installation of a source removal system at Building 96; the off-site Industrial Complex IRA treatment system; an on-site and off-site pump and treat system; the continued operation of the on-site Southern Boundary IRA treatment system; off-site public water hookup; and the implementation of a groundwater monitoring program. This alternative will have the same configuration of wells as Alternative V10b. However, instead of in-well stripping, the groundwater will be extracted using standard recovery wells, transferred on-site via underground piping, and treated by an air stripper. The treated groundwater will be discharged on BNL property to the OU III Basin next to the HP Basins.
E.4.2 Comparison Analysis
Each of the remedial alternatives were evaluated against the following seven criteria: (1) overall protection of human health and the environment, (2) compliance with ARARs, (3) long-term effectiveness and permanence, (4) reduction of toxicity, mobility, and volume, (5) short-term effectiveness, (6) ability to implement, and (7) cost. CERCLA requires the evaluation of the alternatives against nine considered criteria, however, the "State Acceptance" and "Community Acceptance" criteria will not be evaluated until comments from the regulatory agencies and the public on the FS Report have been received. To the maximum extent practical, CERCLA requires that remedial action alternatives must (1) be protective of human health and the environment, (2) attain ARARs, (3) be cost effective, (4) use permanent solutions and alternative treatment technologies, and (5) reduce toxicity, mobility, or volume. Once each of the alternatives was individually assessed against the seven criteria, a comparative analysis of them was made. The comparative analysis is summarized below.
E.4.2.1 Comparative Analysis of Strontium Remedial Alternatives
This section discusses the key factors and differences among the remedial alternatives for strontium relative to each of the evaluation criteria. Table E-2 summarizes the results for each of the seven evaluation criteria.
Short Term Effectiveness
The No Action Alternative (S1) does not include any disturbance, site access or use of the site and, therefore, does not pose any additional risks to the community or on-site workers from the potential release of contaminants.
Alternative S2, Natural Attenuation, consists of allowing the natural processes of radioactive decay, diffusion, dilution and adsorption to reduce the concentration of Sr-90 in the groundwater to the acceptable level. Short-term risks are limited to the possible exposure to workers to contaminated soil and groundwater when installing monitoring wells and groundwater sampling. In the short term, this alternative involves minimal exposure to Sr-90 of construction workers or the community.
Alternative S4, the In situ Precipitation alternative, will require drilling of 55 injection wells and mixing and injecting of immobilization chemicals into the aquifer to trap the Sr-90. Some risk exists from the construction and from the drill cuttings. Accidents and exposure can be prevented with training, and by using protective equipment.
Alternative S5a, Groundwater Extraction/Ion Exchange/On-site Discharge, the "pump and treat" remedy, involves extracting of groundwater from two areas of high Sr-90 concentration (WCF/PFS and Glass Holes), and treating and discharging it to on-site recharge basins. This alternative results in immediate control of the migration of the highest Sr-90 concentration areas and reduces Sr-90 concentrations in the aquifer. Installation of this system presents some risk to on-site workers through dermal contact, ingestion or inhalation of groundwater and/or soils during construction and O&M activities. However, exposure can be prevented by using personal protection equipment.
Alternative S7, Groundwater Extraction/Ion Exchange/On-site Discharge/Permeable Reactive Wall, the "Hybrid" alternative, includes the "pump and treat" system at the WCF/PFS area and the installation of a PRB at the Glass Holes area. This alternative requires the management of over 2,000 cubic yards of excavated soil, including up to 1,000 yards of soil from the aquifer that may be radioactive. This soil must be managed to prevent exposure of construction workers and to prevent movements of dust.
Alternatives S1 and S2 will reduce concentrations of contaminants through natural decay, dilution, and adsorption. Alternative S4 enhances adsorption of the pollutants to prevent its migration. The groundwater transport modeling shows no impact on potable water wells or BNL and supply wells over a 60-year period. The concentration of Sr-90 within the plumes are, reduced over the long-term.
For Alternatives S5a and S7, the concentrations of Sr-90 are reduced to the MCL within 30 years at the WCF/PFS area. In addition, Alternative S5a of the Glass Holes area will be cleaned up within 8 years. The treatment systems will generate residual waste from the ion exchange technology. The residuals will be managed and disposed off-site as low level radioactive waste. Exposure to waste can be minimized through proper training of personal and using personal protection equipment to reduce long-term risk of exposure. For Alternative S7, the PRB will adsorb Sr-90 from the plume for at least 25 years and immobilize the adsorbed Sr-90 within the wall until its radioactivity decays.
Reduction of Toxicity, Mobility, and Volume
Alternative S1 does not use treatment or containment to reduce the toxicity, mobility or volume of the Sr-90 in the groundwater. In Alternative S2, the Sr-90 concentrations will be reduced by natural decay, dilution and adsorption. Minimal migration of contaminant is supported by the results of groundwater modeling and long-term monitoring in Alternative S2. Transport through the aquifer is minimal, and the bulk of the contamination remains within the same area in the water table zone of the Upper Glacial aquifer.
Alternative S4 and the PRB component Alternative S7 reduce the mobility of the Sr-90 by in-situ treatment. Reduction in toxicity and volume are achieved by natural decay. Alternative S5a and the WCF/PFS component of the Alternative S7 use extraction and treatment systems to reduce the toxicity, mobility, and volume of the contaminated groundwater to below the 8 pCi/l MCL. The Sr-90 removed from the groundwater will be adsorbed on the zeolite media within the groundwater treatment system, and transported off-site for permanent disposal. There are no significant advantages for Alternative S5a over Alternative S2 or S4 in preventing migration of the plume because of the low mobility of the Sr-90.
The No Action Alternative S1 requires no further activity. The Natural Attenuation Alternative S2 will require a public awareness and monitoring program, both of which can be easily implemented. The In situ Precipitation Alternative S4 requires drilling injection wells and mixing and injecting chemicals to immobilize the Sr-90. All activities associated with this alternative are readily available and proven, although avoiding underground utilities and pipelines in the WCF/PFS area will require extensive planning and detailed surveys. A treatability study will be required to confirm the parameters necessary for stabilizing the Sr-90. Alternative S5a will require constructing of treatment systems, extraction systems and discharge lines. The equipment required for treatment is readily proven and commercially available. A treatability study will be conducted during the remedial design work to confirm that Sr-90's loading and removal kinetics are as expected and that the 8 pCi/l MCL can be met. Sampling for effectiveness of treatment and groundwater monitoring also will be needed and can be easily implemented.
Installing the PRB for Alternative S7 will be difficult. It requires not only excavating an 80-foot deep trench under slurry and placing 1,039 cubic yards of clinoptilolite in the trench, but also managing over 2,000 cubic yards of excavated soil, including up to 1,000 yards of soil from the aquifer that may contain some radioactivity. Exposure of construction workers to the soil must be prevented, as must the release of dust to the atmosphere.
Appendix D contains detailed cost tables for these alternatives summarized in the table below. There are no costs associated with Alternative S1. Installation of monitoring wells, groundwater sampling and analysis, and groundwater modeling are included in all other alternatives. Alternatives S4 and S5a cost an additional $1,000,000 to $5,000,000 to Alternative S2, and no significant advantages were observed in implementing these alternatives over natural attenuation, due to the low mobility of Sr-90 and the lack of impact on the receptor.
Compliance with ARARs
Alternatives S5a and S7, as well as the In situ Precipitation Alternative S4 will bring all locations impacted by Sr-90 into compliance with chemical-specific ARARs within 30 years; therefore, these alternatives comply with RAOs for restoring the aquifer within 30 years. In the Natural Attenuation Alternative S2 and the No Action Alternative S1, ARARs are not achieved within 30 years. The Glass Holes area declines to the MCL in approximately 40 to 50 years, and the WCF/PFS area in approximately 60 to 70 years. However, mobility and growth of the plume are negligible at all locations during this time period.
Through design and permitting of the Sr-90, Alternatives S5a and S7, the discharge of the treated Sr-90 will comply with all applicable chemical-specific and action-specific ARARs by using proven technology and design.
Overall Protection of Human Health and the Environment
The Natural Attenuation alternative protects human health or the environment over the long-term since groundwater modeling simulations show no effect on any potential receptors. However, the Natural Attenuation alternative requires 60 years for Sr-90 to naturally decay to ARARs. The No Action alternative cannot address the future protection of human health and the environment due to the lack of long-term monitoring and modeling data. The In situ Precipitation Alternative S4 gives added protection to the environment since it reduces the mobility of Sr-90.
Alternatives S5a and S7 also protect human health and the environment by remediating the Sr-90 contaminated groundwater to the MCL within 30 years.
Protection of human health can be measured by both the impact of the remediation scheme to the aquifer and the environment, and the impact of the consequences of the remedial alternative.
Although Alternatives S5a and S7 result in restoration of the aquifer, the potential exposure to contaminants has been increased. Additionally, these alternatives generate radiological waste which must be managed, transported, and disposed off-site, all of which increase potential exposure. Because of the low mobility of Sr-90 at both the Glass Holes and WCF/PFS areas, no potential impacts to receptors is anticipated, and all Sr-90 contamination will remain within the boundaries of BNL.
E.4.2.2 Comparative Analysis of Remedial Alternatives for Tritium
This section discusses the key factors and differences among the tritium remedial alternatives relative to each of the evaluation criteria. Table E-3 summarizes the results for each of the criteria.
Short Term Effectiveness
Alternative T1 does not include any disturbance, site access or use of the site and, therefore, does not present the community nor on-site workers with any additional risks resulting from potential release of contaminants.
Alternative T2, Natural Attenuation, consists of allowing the natural processes of radioactive decay, diffusion, dilution, and adsorption to reduce the concentrations of tritium in the groundwater to acceptable levels. Short-term risks are limited to possible exposure of worker to contaminated soil and groundwater when sampling groundwater. In the short term, this alternative allows the tritium plumes to migrate further, although tritium is rapidly attenuated by decay and dispersion.
Alternative T3, Natural Attenuation with the operation of the tritium IRA is similar to T2; however, operating the IRA may increase the potential exposure of workers since the groundwater is extracted and then discharged to an on-site recharge basin. In Alternative T5, containment by recirculation, groundwater from the southern edge of the 20,000 pCi/l contour is extracted and pumped upgradient to the RA V recharge basins. This limits the migration of this part of the plume, and minimizes the volume of the aquifer that exceeds the MCL for tritium.
Alternatives T4, T6, T7, and T8, the "hot spot" remedies, involve extracting groundwater from the areas of high tritium concentration within the plume and treating it (by on-site storage, off-site evaporation, or on-site evaporation). All these alternatives present some risk to on-site workers through dermal contact, ingestion, and inhalation from construction, regular operation, and maintenance. However, exposure can be minimized by using proper work practices and procedures.
In all alternatives, the time to remediate to MCLs within the aquifer is equal to, or less than, 20 to 25 years. There are no significant reductions in the time taken to reach MCLs when active remediation is implemented (T5, T6, T7 and T8).
Alternative T1, Alternative T2, and Alternative T3 will reduce contaminant concentrations in groundwater via natural attenuation (decay, dilution, and diffusion). For natural attenuation, groundwater transport modeling predicts no impact to potable-water wells or BNL supply wells. The concentrations of tritium within the plume are attenuated by decay and dispersion to below the drinking water standard over 20 to 25 years. Continuation of the IRA re-circulation system does not enhance natural attenuation.
Since the No Action Alternative T1 does not include modeling or monitoring, its long-term effectiveness cannot be verified.
Alternatives T6, T7 and T8, hot spot extraction of tritium groundwater and on-site storage, off-site evaporation, or on-site evaporation; will remove significant amounts of tritium from the aquifer. However, no significant reduction in duration of cleanup was observed when these alternatives were compared to Alternative T2. Based on modeling simulations, the cleanup time is only reduced by approximately five years, with no significant reduction in the overall plume migration. This is also true of the Contingency-Based Remediation Alternative T4. For Alternatives T4, T7, and T8, the long-term risks due to possible exposure to tritium in the atmosphere are increased from discharging tritium to the atmosphere. This risk is not significant.
Reduction of Toxicity, Mobility, and Volume
Neither the No Action Alternative (T1), continuation of the IRA (T3) nor Natural Attenuation (T2) uses treatment or containment to reduce the toxicity, mobility, or volume of tritium in the groundwater. The tritium concentrations will be gradually reduced or attenuated by natural decay, dilution, and dispersion. Slight movement of the contaminant will continue because groundwater is not contained nor treated. Alternatives T4, T6, T7 and T8 extract hot spots to reduce the toxicity, mobility and volume of contaminated groundwater, removing tritium permanently from the aquifer.
None of the extraction alternatives (T3 through T8) noticeably affect the migration of tritium compared to the Natural Attenuation Alternative, T2. In all alternatives, tritium levels greater than the MCL will not migrate past Princeton Avenue.
Alternatives T1 and T2 will require a public awareness program and natural attenuation will require monitoring, both of which can be easily implemented. Alternatives T4 through T8 will require building storage tanks, carbon units, extraction systems, and discharge lines. The equipment required for treatment is readily proven and commercially available. Sampling for effectiveness of the treatment and groundwater monitoring can be easily implemented. The alternatives associated with off-site disposal, T4 and T7, may encounter some difficulties in obtaining approvals for transportation and off-site evaporation which delay the implementation of this alternative. Additionally, the on-site storage and on-site evaporation alternatives may encounter problems with community acceptance that could complicate or delay implementation.
There are no costs associated with the no action alternative. All other alternatives include costs associated with the installation of monitoring wells, groundwater sampling and analyses, and groundwater modeling.
The following is summary of the capital and operational costs associated with all the alternatives except No Action.
The alternative with the lowest capital cost is Alternative T2, since all the wells required for monitoring natural attenuation have been installed. Alternative T6, groundwater recovery with on-site storage has the highest capital costs mostly associated with constructing a large storage tank.
The alternative with the lowest operational and maintenance costs is alternative T2. Alternative T7 has the highest costs because of the expense of transporting and disposing of approximately one million gallons of tritiated groundwater at $20 per gallon off-site.
Compliance with ARARs
Compliance for the No Action Alternative T1 with the chemical-specific ARARs cannot be documented. Groundwater tritium quality is projected to be in compliance with ARARs after 20 to 25 years, but this cannot be confirmed due to the lack of groundwater monitoring in this alternative. Therefore, compliance with ARARs is not achieved. The Natural Attenuation alternatives, as well as Alternatives T4 through T8, comply with ARARs within 20 to 25 years. Dilution and decay reduce tritium concentrations to below the MCL of 20,000 pCi/l. Groundwater discharge standards (chemical-specific and action-specific ARARs) for tritium and VOCs will be attained by all alternatives using extraction.
The on-site evaporation alternative will require approval from regulators due to the discharge of tritium to the atmosphere. However, the discharge concentrations will be substantially below the existing limit for the HFBR Stack.
Overall Protection of Human Health and the Environment
Based on the results of groundwater modeling, Alternative T1 will not ensure that human health and environment will be protected because even though the contaminant plume is predicted to attenuate to below chemical-specific ARARs before moving off BNL's property it cannot be confirmed, due to the lack of groundwater modeling. Therefore, overall protection of human health and the environment is not achieved.
Alternatives T2 through T8 protect human health and the environment. Tritium concentrations are rapidly reduced by dispersion, dilution, and decay. For the natural attenuation alternative, 20 to 25 years is required for the aquifer concentrations to meet the 20,000 pCi/l MCL. No impact to potential receptors is predicted, and groundwater with tritium levels higher than the MCL will not pass Princeton Avenue for any alternative.
Alternatives T4, T5, T6, T7 and T8 require the extracting and handling of tritiated groundwater which can potentially increase the exposure rate to tritium. Transportation under Alternatives T4 and T7 also increase the chance for exposure due to the large travel distance required for off-site disposal of the tritiated groundwater. Evaporation alternatives T4, T7, and T8 also increase exposure to tritium by discharging it to the atmosphere.
E.4.2.3 Comparative Analysis of Remedial Alternatives for VOCs
This section discusses the key factors and differences among the VOC alternatives relative to each of the evaluation criteria. Table E-4 summarizes the evaluation criteria for each of the alternatives.
All alternatives, except V1, include the operation of the Southern Boundary system, Industrial Complex IRA system, and a source removal action at the source area near Building 96. The majority of alternatives which include additional treatment use in-well stripping to further treat VOC contaminated groundwater. Alternative V13 uses traditional "pump-and-treat" technology to capture, contain, and treat groundwater on-site and off-site. Based on the groundwater modeling simulations, specific areas on-site and off-site were identified as locations where additional treatment will occur. On-site locations include the source area at Building 96, Middle Road, and at the low level VOC plume at the southern boundary. Off-site locations include LIPA's right-of-way, Industrial Complex East, North Street/Sleepy Hollow, RA V plume, Brookhaven Airport, and the low-level VOC plume at Industrial Complex. These locations were identified as ideal for additional treatment of VOCs based on land availability, the presence of high VOC contaminants, or the need to contain the VOCs to prevent their further downgradient migration. The VOC alternatives have been developed based on varying the number and location of wells within these specific areas and determining the impact on the VOC plume based on groundwater modeling. However, during the detail design of the preferred alternative, the number and placement of the wells might vary based on more detailed modeling and further delineation of VOCs.
Alternative V1 does not include any major active remediation and, therefore, presents the least risk to the community any workers.
Alternative V2, natural attenuation, represents the baseline for the VOC alternatives. It involves installing an AS/SVE system at Building 96, a suspected source area for VOCs, and installing and monitoring additional on-site and off-site monitoring wells to assess natural attenuation. Alternative V2 also includes the installation and operation of an off-site IRA along with operation and maintenance of the Southern Boundary IRA treatment system. The operation of the IRAs, the AS/SVE treatment systems and a natural attenuation program are remedial components in all the alternatives except Alternative V1. These components pose some exposure risks to on-site workers through dermal contact, ingestion, and inhalation of contaminants during construction and operations of systems. However, exposure can be prevented by using proper personal protection equipment. All alternatives except V1 produce process residuals (spent carbon) as a result of the source remediation system at Building 96 which will require proper handling. The alternatives involving in-well stripping (V7, V10b, V10c, and V11) pose the least short-term risk to workers and to the community during installation because such systems require less extensive construction, require minimal contact with groundwater, and generate fewer process residuals. However, potential emissions of the contaminants, and noise from off-site sparge systems located in residential areas may be a concern for the community. These impacts will be minimized by engineering controls, such as off-gas treatment and system enclosures. Alternative V13 includes extraction of groundwater for treatment and discharge. It presents some risk to on-site workers through dermal contact, ingestion, and inhalation of contaminants during construction activities and system operation. These risks can be reduced by using personal protection equipment and trained personnel.
Alternative V1 will not significantly reduce contaminant concentrations nor limit the migration of contaminated groundwater. All other alternatives actively treat the groundwater. Migration, plume growth, and discharge levels of VOCs to the Carmans River are the highest in this alternative as compared to all others.
Alternative V2 includes operating the on-site and off-site IRAs along with the operation of an AS/SVE system for the VOC source area. This baseline alternative results in no further impacts to the aquifer from VOCs at the source area, as well as maintaining VOC plume migration control at the boundary and at the Industrial Complex. Groundwater modeling simulations show that the MCL is not reached on-site and off-site of BNL within 30 years. However, significant reductions in the extent of the plume are observed.
Model simulations indicate that Alternatives V7, V10b, V10c, V11 and V13 will be very effective in the long-term for reducing contaminant concentrations and mobility due to the high remedial effort applied. They are the most effective in removing and reducing VOC concentrations in the aquifers.
Alternative V11, which involves treatment through in-well stripping wells in non-residential areas, requires more time to achieve the MCL than other alternatives that include off-site wells within residential areas (except for V7). Alternatives which include remediation wells within plume hot-spots, regardless of residential areas, give an accelerated remediation schedule and effective remediation of the Upper Glacial aquifer in 30 years.
Alternative V7 is the least aggressive methodology with a capture goal of concentrations greater than, or equal, to 250 ppb within the defined hot-spot areas. However, it includes the reduction and capture of VOCs within the OU III low level VOC plume and RA V plume. This alternative also includes installing wells at Brookhaven Airport to prevent migration of the plume beyond Flower Hill Drive. Alternative V7 allows the greatest movement of VOCs for the OU III and OU I/IV off-site VOC plumes, with VOCs greater than the MCL still persisting within the Upper Glacial aquifer after 30 years. The implementation of the low level VOC subsystems did not result in significant reduction in plume migration or Carmans River discharges as a result of the low level VOC plume.
Based on 60-year groundwater modeling of the Magothy Aquifer, VOCs will still be present above drinking water standards for all alternatives.
Reduction of Toxicity, Mobility, and Volume
All alternatives (except V1) include the operation of the southern boundary treatment system, off-site Industrial Complex IRA, the installation and monitoring of additional on-site and off-site monitoring wells for the natural attenuation and removal of the VOC source at Building 96. Groundwater modeling shows that these remedial components alone reduce the contaminant's volume and mobility and prevent their further migration past the property line at concentrations greater than 50 ppb. Natural attenuation significantly lowers concentrations of contaminants in the aquifer for the on-site VOC plume during the 30 year operation of the southern boundary treatment system.
Off-site treatment as in Alternatives V7, V10b, V10c, V11 and V13 effectively reduces the toxicity, mobility, and volume of off-site VOCs, and prevents their significant migration. Potential discharges to the Carmans River are also reduced. However, even with the aggressive off-site treatment in Alternatives V10b, V11 and V13, small discharges (less than 5 ppb) are simulated to occur within 30 years. Alternatives with no off-site treatment had simulated VOC discharges to the Carmans River between 5 ppb and 15 ppb. Natural attenuation which is a component of all the alternatives, reduces contaminants over time. Biodegradation of chlorinated VOCs is evidenced by the presence of daughter products of parent contaminants. However, the VOC simulations conducted in support of the alternatives did not include any biodegradation of VOCs.
Alternatives V10b, V10c, and V13 restore the Upper Glacial aquifer to the MCL in approximately 30 years, and result in the greatest reduction in the contaminant's toxicity, mobility, and volume. Therefore, these alternatives comply with the RAOs presented in this FS Report. The amount of time required for Alternative V7 to restore the Upper Glacial aquifer exceeds 30 years.
From a technical standpoint, all the alternatives can be implemented. Pump-and-treat and in-well stripping technologies have been demonstrated either on-site or at other contaminated sites. Equipment, contractors, and vendors required to install the remedial components are available. In-well air stripping was demonstrated to be effective in reducing contaminants to discharge standards in field pilot tests at BNL.
Administratively, it will be difficult to implement the off-site alternatives due to regulatory approval, public acceptance, and the requirements for property access for the installation of the treatment systems. Alternative V13 will be the most difficult to implement administratively because it will involve installing underground extraction piping through major roadways (e.g., Long Island Expressway), residential areas, and industrial areas. In-well air stripping systems will require LIPA's approval for all alternatives except alternative V11. All remedial alternatives will require compliance with Air-Guide-1 air-discharge limits for the air strippers, the in-well stripping systems, and the AS/SVE system. Compliance can be easily demonstrated by using off-gas treatment where appropriate. An off-gas treatment system (carbon adsorption) was proposed for systems with high VOC contamination for wells located in residential areas.
All VOC alternatives can be implemented in phases. North Street and RA V subsystems can be designed and implemented first. The LIPA and Industrial Park East subsystems can be implemented next, and finally, the Brookhaven Airport subsystems can be implemented, because contamination has not reached these subsystems.
All VOC alternatives (except for V1) included costs for operation of the southern boundary and Industrial Complex IRA systems. These alternatives also include capital and O&M costs associated with the source removal system at Building 96 and for natural attenuation/groundwater monitoring.
Southern boundary costs were included because on-site treatment at Middle Road affected the net present worth cost of the southern boundary treatment system by influencing the operating time frames. The implementation of on-site treatment at Middle Road reduced the cost of operating the southern boundary treatment system by reducing its operating duration from 30 years to 15 years.
Although Alternative V7 is based on a capture of 250 ppb, its cost is higher than the alternatives V10b and V10c because it addresses the RA V and OU III low level VOC plume with an additional 8 off-site in-well stripping wells. These plumes are remediated with fewer wells in the other alternatives.
The following table summarizes the capital, operation and maintenance, and total net present worth cost for each of the alternatives by component:
Alternatives V10b and V10c, have comparable cost to one another. Well-configuration is similar in Alternatives V10b and V13. Although alternative V10b and V13 are comparable with regard to well placement, Alternative V13 has the higher cost because of the installation of the pipeline required to transfer the groundwater on-site for treatment. The VOC alternative with the lowest cost is alternative V2 (natural attenuation); the one with the highest cost is V7.
Compliance with ARARs
Alternatives V1 and V2 do not achieve chemical-specific ARARs for the on-site and off-site VOC contamination because Federal MCLs and state groundwater standards will still be exceeded after 30 years. Alternatives V10b, V10c, and V13 remediate the groundwater in the Upper Glacial aquifer within 30 years and, therefore, are in compliance with ARARs and RAOs. Alternative V7 does not comply with chemical-specific ARARs because VOC concentrations exceeding the MCL still persist within the Upper Glacial aquifer after 30 years. None of the alternatives remediate the Magothy within 30 years. In fact, based on long-term modeling, VOCs will be present in excess of 100 ppb within the Magothy aquifer for the next 60 years. However, migration and growth of the plume within this aquifer is minimal.
Alternatives requiring discharge of water or air will comply with chemical-specific and action-specific ARARs at the discharge point through engineering controls and monitoring.
Overall Protection of Human Health and the Environment
All alternatives, except V1, include operation of the southern boundary treatment system, off-site Industrial Complex IRA, hookup of residential homes to public water downgradient of the BNL site, the installation and monitoring of additional on-site and off-site wells and removal of the VOC source at Building 96. Therefore, all these alternatives will provide some protection of human health and the environment by minimizing exposure pathways. Alternatives with off-site treatment (V7, V10b, V10c, V11, V13) protect human health and the environment because they offer a high reduction in the contaminants concentrations and mobility. Overall, these alternatives provide better protection of human health and the environment by removing the contaminants from off-site groundwater to PRGs and by allowing contaminant levels in the aquifer to reach MCLs within 30 years. Alternatives V10b and V10c provide the greatest amount of protection by reducing contaminants both on-site and off-site and they comply with ARARs in 30 years.
All treatment alternatives require long periods to remediate (25 years to more than 30 years). In the case of Alternative V1 and V2, contaminated groundwater will continue to migrate, so that human health and the environment will not be protected. However, by establishing a risk management program, including groundwater monitoring, residential well monitoring, and public water hookups, risks posed by the VOCs to human health and the environment can be minimized, under natural attenuation.
For those alternatives that implement off-site remediation, groundwater modeling indicates that the VOC contaminants will discharge to the Carmans River at low concentrations (i.e., less than 5 ppb). Discharge into the Carmans River from the OU III and OU I/IV plumes will be less than 1 ppb, while the discharges resulting from the low level VOC plume is less than 5 ppb.
Alternatives with air emissions will be evaluated for compliance with appropriate air regulations (Air Guide-1). Those not passing air discharge screening will have off-gas treatment before their release. Preliminary evaluations indicate that the hot spot remedial sub-systems such as the Industrial Complex East, LIPA subsystem, and the North Street sub-systems that are components to alternatives with off-site treatment, will require off-gas treatment.